The infusion of red blood cells (RBCs) into the fetus is one of the most successful means of in utero therapy. Although never studied in randomized trials, there is no doubt that this technique has contributed to survival of the severely anemic fetus. Universal use of Rh(D) immune globulin has dramatically reduced the need for intrauterine transfusion; however, the procedure continues to be an essential modality for treatment of severe fetal anemia from a variety of causes.
Sir William Liley first introduced the concept of intrauterine transfusion (IUT). While working in New Zealand, he learned from a visiting fellow that RBCs infused into the peritoneal cavity of African children with sickle cell disease appeared to migrate into the intravascular space and correct their anemia . Liley postulated that peritoneal infusion (IPT) of RBCs could also be used to transfuse the severely anemic fetus. Since ultrasonography was not yet available, these early procedures were 'guided' by radiographs or fluoroscopy. Fetal position was determined by a variety of techniques, such as using radiopaque dyes to delineate fetal bowel, placing metal markers on the maternal abdomen to indicate fetal position, and inserting needles to immobilize the fetus.
Static gray scale ultrasonography was first used in conjunction with IUT in 1975, and replaced by real-time ultrasonography in 1977. The next major advance was in 1981 when an intravascular transfusion (IVT) was performed by inserting the transfusion needle directly into a fetal vessel on the placental plate . Currently, the standard method of fetal transfusion uses an umbilical vessel or the intrahepatic portion of the umbilical vein for direct access to the fetal vasculature.
General approach — Intrauterine transfusion of RBCs is indicated to prevent fetal death from severe anemia. The procedure is generally limited to fetuses between 18 and 35 weeks of gestation because of technical limitations before 18 weeks and excessive fetal risk compared with delivery and postnatal transfusion after 35 weeks (see 'Gestational age at first transfusion' below).
Normal fetal hemoglobin concentration increases linearly during pregnancy, from about 10 to 11 g/dL at 17 weeks to about 14 to 15 g/dL at term, one standard deviation is approximately 1 g/dL (table 1) [3-5]. Severe fetal anemia has been defined in a variety of ways: